This study seeks to gain new information on why young women with anorexia nervosa are predisposed to early bone loss and osteoporosis. Through a randomized treatment trial in which participants will receive either combined therapy with the adrenal hormone, dehydroepiandrosterone (DHEA) and estrogen replacement therapy or placebo, we will determine the effects of an 18-month treatment course on bone mass, circulating markers of bone turnover, and serum levels of a factor, insulin-like growth factor I (IGF-I). We are also studying if these therapies change bone structure to increase skeletal strength compared to placebo, as assessed through cross-sectional geometric analysis of our bone density data by dual-energy x-ray absorptiometry (DXA).